Memory
by PythianPickles
Summary: No one, not even Kamijou Touma, can forget ten thousand worlds. But a certain someone can help him with that - in a way neither of them ever expected.


**AN: I always thought that Kazuma-san kind of glossed over the effect of going through Othinus's ten thousand worlds of doom and gloom - surely even the Touman couldn't just shrug that off! Although I understand why - there is a story to tell, after all, and Index has always been about action - it always left me with the feeling that there was a bit of a hole in the story.**

 **This is my attempt to explore that.**

* * *

 **1**

Desert.

The dream took place in the desert this time, and he struggled and flailed in the sand, trying to move the last stubs of his ruined legs before the heat of the sun finally woke him up—

When he opened his eyes, Kamijou almost expected to feel more sand shifting against his arms, spilling out of his bathtub. Instead, the only sensation that greeted him was a cool rush of air, courtesy of his miraculously working air conditioning. It was a good thing it was on; his body was covered in a sweat that had nothing to do with the temperature of the room.

And there he'd been, thinking that tonight would be different—that there would be no dreams.

Then again, that wasn't entirely accurate. His problem had never been with dreams. It had been with memories, memories of a billion worlds and a billion deaths.

Before he knew what he was doing, he was out of the bathtub and sitting on the bathroom's tiled floor, staring at the faint bar of moonlight leaking in from the living room. He'd never felt suffocated by his "bed" before—it was just a place he had to sleep, better for both him and Index—but now, he almost couldn't stand it. Not after sleeping in spaces a hundred times larger, and being buried in spaces a hundred times smaller.

With a _clunk_ , Kamijou let his head fall against the side of the bathtub, letting the sliver of light slide to the bottom of his vision. It would be a huge waste of time to try and sleep again, at least from what the past three nights had told him.

At this point, he wasn't even sure if he wanted to.

Eventually, after sitting in the darkness for what felt like forever, Kamijou stood up. One way or another, he wasn't staying here tonight. He knew that much. There was no longer the fear of discovering countless grains of sand beneath his fingers, but this space still felt too small, too dead.

Space. Maybe that was what he needed now.

There wasn't any need to worry about the floor creaking, not with it being made of hard tile, but Kamijou still took care to tiptoe as he inched towards the bathroom door. Once he reached it, he grasped the knob and turned it slowly, easing it open.

There was a part of the room he needed to see before he ventured out into the living room—the digital clock. Carefully, he increased the opening inch by inch, and then stopped as his target came into view.

 _1:42._

Kamijou took a breath, and stepped out of the bathroom.

Officially, lights-out in Kamijou's dorm building was given as 22:30, though it would be a miracle to find anyone in the complex actually paying attention to it (and even more of a miracle to find the dorm manager enforcing it). Even so, both Index and Othinus generally kept to the rule—apparently it took a lot of energy to survive as either a walking library or a fifteen-centimeter immortal—which meant that at this time, it was pretty safe to say that both were out cold.

Which was just what Kamijou needed. Normally he wouldn't mind their presence too much, but right now he felt an overwhelming need to sort out the tangle in his head by himself. After all, the real problem lay in his memories, and no one—not even Othinus—shared those.

Not to the extent that he needed, anyway. And Kamijou wasn't sure if he wanted to discuss his problems with the entity that had created them in the first place, at least not now.

A few minutes later, the door to a certain apartment was eased open and then closed, as its owner headed out into the night.

Even at this time, Academy City was awake.

* * *

Kamijou had roamed the streets of District 7 enough times to know where and when the people tended to gather. Tonight he avoided all those places, electing instead to stick to the emptier areas. Even so, every now and then a car or security robot would roll by, and he was forced to dart into the nearest alleyway or hide behind a trash can. It was way past curfew, even for the most laidback of schools. The sight of a student like him would only mean awkward questions.

There were still too many people. He felt hunted, even in the place that he'd called home for years now. If anything, that prison of a bathroom had been better than this.

And so, almost without knowing it, Kamijou wandered away from the center of District 7 like a moth in reverse. The farther he went, the less people he encountered—which he'd known would be the case, it was 2 in the friggin' morning—but he didn't stop.

There was a place he'd seemed to decide on, mostly unconsciously—one that had attracted no visitors, even after countless blasts of billion-volt lightning and glowing streams of molten arcade coins.

* * *

When Kamijou finally wandered to his destination, he saw what he had expected to see—an empty bridge, not a car or person in sight. Even in all those other worlds, more often than not this place had been one of the least-travelled areas of Academy City, almost as if it generated one of those people-clearing fields that magicians were so fond of.

 _Those other worlds._

Kamijou found a suitably rust-free stretch of railing and leaned against it. There wasn't much of Academy City to see from here, but that was perfectly fine with him.

No—that wasn't just fine, it was better. The closer he was to _those_ places, the closer Kamijou was to remembering them as they had been: not just as buildings of light and steel, but of molten red and burnt flesh, of hate-filled faces and desolate cold. These weren't memories to treasure. At worst, they would swallow him. At best, he could only try and come to terms with them.

Now, at least, he had the some of the time and space to do so…even if he had no clue how to start. No one would bother him out here. He would spend as much time as needed before going back and trying for some rest—

Then the footsteps started to sound, ringing dully against the bridge's surface.

Well, shit. He should've expected his misfortune to provide him with some company. It seemed even this place wasn't immune to its influence.

As casually as he could, Kamijou straightened, turned, and began moving away from the footsteps. The idea of their owner being a member of Anti-Skill didn't really worry him; he'd seen enough arrests and chases to know that they would've announced their identity almost immediately—especially after seeing a scruffy-looking delinquent like him. And of course Judgment was out of the question, at a time and place like this.

No, Kamijou was more worried about the very real possibility that a fellow delinquent with somewhat more…flexible…morals had decided to join him on the bridge. Now was not the time for a fight, not when he wasn't even sure that he wanted to protect himself. The easiest solution would just be to leave.

Behind him, the footsteps slowly broke off, before ceasing altogether as the person seemed to stop in their tracks. Had they seriously just come out here to enjoy the view? Maybe this place's people-clearing effect wasn't as strong as he'd thought.

And, right on cue, the footsteps broke into a dead run.

Okay, now this was what he'd been expecting! Kamijou tensed, prepared to sprint for it—

"Hey! Hey, you! What're you doing out here?"

—and stopped.

He knew that voice. He knew it very well. It belonged to the one other person who seemed to be immune to this bridge's mysterious aura. But still, that raised a bigger question…

"What are _you_ doing out here?" Kamijou asked, turning to face the person as he spoke.

Sure enough, there stood Misaka Mikoto. It was still a little difficult to see her fully, but he could make out enough of her features to recognize her, from the short brown hair to the Tokiwadai—wait, what?

Kamijou stared.

"That's…that's none of your business!" Mikoto yelled, as she continued to run towards him. "Besides, you idiot, you shouldn't even be…wait." She'd apparently gotten close enough now to see his face clearly, because she raised an eyebrow and asked, "Why are you staring at me like I've got something on my face?"

With some alarm, Kamijou realized that he was, in fact, gawking like a three-year-old. "I-It's nothing," he said, shaking his head and hurriedly turning his gaze to the river. "It's just…you look different. Without the whole…Tokiwadai getup." Really, he reminded himself furiously, it _was_ nothing. Really. He'd just been surprised, that was all.

"What are you talking about?" Mikoto still had an eyebrow raised; it stayed there as she leaned on the railing beside him and looked out towards the river. "It's not like this is the first time you've seen me out of uniform. There was Denmark, all that time in Hawaii, and the time you broke into my violin recital, and then the Daihasesai…and probably some other time I don't remember. So what's really happening here?"

Kamijou groaned. "I already told you," he said, staring fixedly at the river. At the moment, he was considering jumping down and going for a swim—anywhere away from here. If he was honest with himself, he couldn't really understand his own reaction. It seemed like his unconscious had really been trying to torture him recently—first with the memories, and now these unexplainable reactions. He wouldn't have been surprised if hallucinations were next.

"Something wrong?" Mikoto was looking at him now. "Come on, I've seen that expression before, and it's always been because you've done something stupid. Or…hold on!" Her expression brightened. "Is it someone else? I can always go and have a little _talk_ with them—I'll even be nice and let you get a few punches in."

Oh, if only this were a problem he could just punch away. "It's nothing like that," Kamijou said, closing his eyes. For some reason, he felt he couldn't afford to meet her gaze. "There was just something I needed to figure out, and…"

He hesitated. _I can't do it with you here_ was the most obvious answer, but it wasn't quite accurate and would definitely prompt a lightning spear or two (even if Mikoto seemed to be holding back for some reason, at the moment). But what else was there to say? God, he couldn't think right now.

 _You could just tell her all of it_ , some part of his mind told him. _She's asked you about this before._

No—because no matter what she had said before, he couldn't believe that Mikoto wouldn't hate him once she discovered the full extent of what he'd cost her. Kamijou valued this…whatever they had going on…too much to do that, as selfish as it was. At any rate, he couldn't stay here—she was the perfect reminder of what had happened, and what he had done.

"Sorry. I need to go," he said finally, pushing himself off the railing. He began to walk away. "See you later, Misaka." Lame, inconclusive, but as long as he could leave…

"Wait."

Kamijou almost paused for a second, before slowly moving forward again. There had been times that he'd failed to hear her before. He could afford for there to be one more, even if his old self would've blinked in shock at what he was doing.

He made it two more steps before he heard the _crackle_ of electricity, and smelled the familiar whiff of ozone. A second later, a couple of sparks blew past his face, raising the hairs as they passed.

"I said _wait_ , you blockhead! I know you heard me!"

Despite himself, Kamijou felt a wry smile appear on his face. Leave it to Mikoto to notice less than a second's worth of hesitation on his part. "Okay, fine," he said, turning to look at her. "I'm sorry for ignoring you, but I really have to go. I…" He looked away for a moment. "I just realized I left the stove on." He looked back at her, and tried to put on an embarrassed smile. "Silly me, huh?"

He wasn't sure if Mikoto bought it fully, but there must have been _some_ effect, as the sparks playing around her bangs slowly fizzled out, along with the anger in her expression. Something—Kamijou couldn't quite tell what it was—crossed her face. "You idiot…" she murmured quietly.

Good enough for him.

He walked past her and started back the way he had come. Even the iron bridge wasn't safe, huh? Well, fine—he supposed he could just find an empty park somewhere, or cram himself into the first alley he came across…

"…hold it."

Mikoto's voice was soft, hesitant; so much so that Kamijou almost missed the words for real this time. He kept going.

"Hold it," she said again, more firmly.

Kamijou shouldn't have stopped. He did.

Quiet footsteps started to sound as, once again, Mikoto made her way towards him. This time, there were no sparks, no spears of lightning, not even an "you idiot." It seemed she'd realized that she'd never needed those to begin with.

When Mikoto spoke, her voice came from directly behind him.

"A long time ago, I was dealing with something terrible, remember? The full darkness of this city. I didn't know it, but fighting that was changing me. I was changing in ways I didn't even notice myself—but one of my friends noticed for me. She tried to ask me what was wrong. And when that happened…I thought about what would happen if she found out. Would she be hurt or killed if she helped me? Probably. Would she hate me? Definitely. So I lied. I made some jokes, put on a bright smile, and told her that her Onee-sama was perfectly fine. I did that to her day and night."

Mikoto gave a bitter laugh.

"So," she said softly. "After all that, do you really think I can't tell what it sounds like when someone else tries that on me?"

There was a long silence. Kamijou tried to think of something—anything—to say in response, but only managed to open his mouth before Mikoto stepped in front of him and blocked his way.

"This is where you saved me," she said, punctuating the _you_ by jabbing his chest with a finger. "And you did it by breaking into my room, searching through my stuff, running all over the place to find me, and generally acting like the biggest creep in the world. Still…" Mikoto broke off and glared fiercely at the ground. "That…was what I needed," she said, gritting her teeth and forcing out each word like she was admitting some terrible secret. "If something like that is what you need tonight, then you better know that I'm ready to do it. Because I know I haven't repaid you yet."

Kamijou sighed. "Look. I'm glad I could help, but—"

In a blur of movement, Mikoto's head flashed back up, and she was glaring straight at Kamijou again. "I don't care what you say. I still owe you for that." Her glare somehow got even fiercer. "Now I'm making sure to pay you back."

"You can zap me all you want tomorrow," he said. "Now, I think I'm starting to smell smoke, so I better get going." He walked around Mikoto; began to pass her…

"Jeez. Looks like I'll have to pay you back with exactly what you gave me, huh?"

 _What exactly was_ that _supposed to mean?_ Kamijou thought—just as he felt a hand close tightly around his wrist. His left wrist. "Wait," he said. "I need to—whooooa!"

Mikoto started dragging him off the bridge to some unknown destination—one in the opposite direction of his escape route. "Don't you remember what I told you in Honolulu?" When Kamijou said nothing, she snorted. "Guess not. Well, you better remember it this time, especially since I'm making a change. That time, I told you we were heading down the same path…but here's the thing, buddy. No one said you were leading the way."

As she said the words, Mikoto practically threw Kamijou onto a bench that he hadn't even known was on the bridge. Then she frowned down at him, hands on hips.

"If you want to keep insisting I don't owe you, fine," she said. "I'll fix that mistake later. Right now, only one thing matters to me." Mikoto sat down beside Kamijou, and looked hard at him. "Something's wrong," she said. "I know that. I knew it even before you tried that stupid line about your stove being on at two in the morning. But..."

She looked away, and Kamijou thought he could see the slightest hint of lightning playing around her bangs.

"You won't tell me about it. You never tell me about it." Her voice was suddenly quiet, devoid of the fire that had been there only moments before. "I'm right here. I want to help you—but you won't let me figure out what I need to do. But I'm pretty sure it has something to do with what happened after we all stepped on Sargasso Island and you flipped sides in a second. I don't know how, but for some reason I always held off asking you about it. I'm changing that right now. So…"

Kamijou sighed. There was no point trying to run from this conversation, not anymore. He'd managed to avoid it even in Denmark, where she'd literally been sitting on top of him, but it seemed that this time she was determined to have it no matter what he told her. And even if she hadn't been the Railgun, Kamijou would've believed that fact to be enough for her to achieve damn near anything she wanted.

Still, that didn't mean he wasn't going to give her a warning first.

"I tried to tell you about this before, after you saved me from those Five Overs in Denmark," he said. He was surprised at how hoarse his voice was; he sounded more like the person who'd been yelling for the past few minutes, as opposed to the one who'd been yelled at. He looked at Mikoto and waited for her to meet his eyes before continuing. "I know you want to help, and I appreciate that. But…I just can'texplain what happened. I couldn't then, and I don't think I could now. I...I'm not even sure I want to."

For a few moments, all Kamijou heard was a slight shuffling as Mikoto fidgeted beside him. She was probably trying to think of something to say and coming up short—not that he could blame her.

Finally, he let out a breath that he hadn't realized he was holding. "Thanks anyway, Misaka," he said. "Don't worry. I'll figure this out." Kamijou gave her a smile; started to get up from the bench. "Besides, I'm sure you have plenty to worry about already, right?"

"I… never said you could leave."

"Eh?" He was stuck halfway off the bench, one hand still resting on the wood. Now he felt he was stuck staring at Mikoto, too.

"You're an idiot, you know that?" she murmured. "You don't just say you can't explain something to me and then try to leave, especially if understanding it is what I need to help you. Can't you see how obvious the solution is?"

Kamijou could only blink at her in consternation.

"Sit down," Mikoto said. "Explain. And don't stop trying until I get it." She finally looked away from him, her face strangely pink. "Idiot," she murmured again.

He'd told himself to avoid this no matter what, seconds ago—and yet now he could only think of one thing to say. "You're going to be here for a while."

Immediately, Mikoto looked back up at him, as if she'd been waiting for even the slightest hint of willingness on his part. "All night, if that's what it takes."

Kamijou couldn't hide the amazement that appeared on his face. For Mikoto to say such a thing—and she had sounded _serious_ about it too, as serious as he'd ever seen her—meant…well, what was it supposed to mean? He wasn't sure if he wanted to think about that.

A second later, she blinked—and this time Kamijou couldn't dismiss the look on her face as anything but a blush. "W-well...maybe not all night!" she yelled, waving her hands wildly. "I-I mean, I'd like some sleep, e-even if there aren't any classes tomorrow, a-and…"

Slowly, Kamijou sat down again. "Well, if that's how it is," he said, "I'll try my best to keep it down to a sentence." He smiled. "Though then you might have a little trouble understanding."

"Shut up," Mikoto muttered, the blush still very much in evidence across her cheeks. "Just start talking already."

The smile dropped off his face. Here it was, then. Kamijou took a breath.

He paused; looked again at Mikoto. She was just sitting there, _waiting_ for him to say more in a way that told him she wouldn't be interrupting anytime soon. Or wasn't intending to, anyway. It would almost have been easier if she was.

Though that would probably change soon.

"In Denmark...I told you that there was a world where all the Sisters had been saved." He looked at Mikoto again, searching for any hint of disbelief in her expression.

She just nodded silently, and kept watching him.

That threw him. He'd been expecting a flurry of questions already, or at least some kind of disbelief—not this _silence_ , whatever the heck it was supposed to mean.

Whatever. Maybe it would help to just say the words without waiting to see what they did. And besides, he hadn't gotten to the part that even he'd struggled to believe—despite the fact that it had been happening right in front of his eyes. "The thing is," he said, "it wasn't just the Sisters who were saved."

And Mikoto finally spoke. "I was with them too, right?" When she saw the surprise on his face, she shrugged. "I remember. You told me this in Denmark. You also said"—she broke off, looked down—"you also said that I was _smiling_. That we were all there as friends." Her eyebrows furrowed. "How could I have done that? After all that happened, _why_ would I have done that?"

"In that world…there was no reason for you not to." Kamijou gave a her a hard look. "Not that I think there's any reason you shouldn't be smiling with them in _this_ world, either."

That didn't make Mikoto seem any less confused. "But how could that be? Why did they even exist in the first place, then? If there was no Level 6 Shift, no Radio Noise—"

"I don't know!" Kamijou was yelling now, and he wasn't sure if he was relieved that Mikoto didn't even flinch. "I'm sorry," he said, more quietly. "But I don't know how any of this was done. I just know what I saw. I saw the Sisters smiling, I saw you smiling, I saw Index smiling, and"—he barely stopped himself before he said _Stiyl_ and _Kanzaki_ —"and everyone else smiling. In that perfect world, everyone was smiling. And I destroyed that."

Mikotostill looked so _confused—_ and he hadn't even begun to explain what had really happened _._

He scrubbed a hand across his face and slumped down on the bench. He'd been afraid of this, trying to explain what had happened and what he felt about what had happened and still explaining nothing at all.

Or maybe he was more afraid of her understanding.

Kamijou couldn't help it—he sighed. It didn't matter how hopeless it made him sound, not any more. "I can't do this."

"Look. I'm sure this is hard..." Mikoto reached toward him for a second, then drew back her hand. "But it's helping you. I know it."

He laughed, once. "You think? It was hard enough, just trying to talk about that world. How am I supposed to explain all the others?"

" _Others?_ " A second later, he heard a sharp breath from Mikoto. "So when you said that a really long time passed between Sargasso and the attack on Othinus…"

"Yeah." Kamijou closed his eyes.

"Just how many _others_ are we talking about here?"

He snorted. "I wasn't exactly keeping count."

Silence from Mikoto. "You're doing it again," she said finally. He heard her take another breath, and this time he definitely heard a few sparks crackling. "You're shutting me out."

"I'm…" Kamijou kept his eyes closed. He had to. "I'm not shutting you out," he said thickly, swallowing hard. "It's just—you know how much time I've spent trying to forget all this ever happened? And now...I can't talk about anything at all anymore." He let out another hopeless laugh. "Pathetic, right?"

"No," Mikoto said quietly. "No, I know what you mean."

And that, of course, was the other issue.

Kamijou had seen death, yes, and watched himself get killed, tortured, and maimed ten thousand times in those other worlds. But the girl next to him had seen the very same…and unlike him, she was still living in the world that those events had created. She would never be escaping that.

Because of his choice.

"Wait!" Mikoto said, nearly yelling the word. Her voice sounded completely different than it had before—it sounded excited now, almost as much as it had back when she'd still been chasing him around.

Kamijou opened his eyes and looked around the bridge frantically, forgetting all about his personal state for a moment. "Is someone else here?" Of all the times for this bridge to betray its nature—

"No, not that!" Mikoto said. "What if you didn't have to explain anything?" Her eyes were shining. "If you remember what happened, maybe you won't have to say anything at all!"

"Misaka. You know that people have to say things to each other if they want to communicate, right? That's why they call it _talk_ therapy—not that I'm saying you're my therapist or anything, but—"

"Just shut up for a second!" Mikoto looked close to hopping off the bench and jumping up and down with glee. "I can't believe I didn't see this before!"

"Uh…" He was stuck staring at the excitement on her face, like an idiot. "Feel like sharing?"

"Look. You know memories are stored in your brain, right?"

"Sure?" He'd had enough somber discussions with Heaven Canceller about his own situation to remember exactly where his memories were (and were no longer) stored. But what did that have to do with anything?

Unless…

"Here's the thing," Mikoto continued, oblivious to Kamijou's slowly widening eyes. "Our brains are a lot like computers, except with neurons as the circuits. And just like a computer, any time your brain needs to access its memory, it uses a pulse of—"

"Electricity." Kamijou let out a long, shaky breath. "It uses electricity."

"Good for you!" Mikoto grinned wider, if it was possible. "Well, if you got that, did you figure out what I was going to say next?" She looked at Kamijou expectantly.

Kamijou hesitated. "I've got an idea," he said slowly. "But…"

It was stupid. It was dangerous. Worst of all, it was impossible. Even by the standards of the city they lived in, it was pure science fiction.

Wasn't it?

"Hey, come on!" Mikoto said, leaning forward in her excitement. She was still grinning. "You can't cop out like that. Worst case scenario, you make yourself look like an idiot, to no one's surprise—"

Kamijou was already too incredulous to feel insulted. "But—" he spluttered. Getting the words out was a struggle. "Even _I_ don't remember everything!" he said finally. "How are _you_ supposed to dig it all out with…with—"

"With my powers?" Mikoto's smile had dimmed slightly, but not for lack of confidence. Kamijou suspected she was simply warming herself up mentally, getting a head start on the calculations. "Easy," she said. "I've done this before."

"You've…what?"

"Long story."

Kamijou's expression remained skeptical.

Mikoto threw up her hands. "It was for a good cause!" she said. "Anyway, forget about that—the important part is, I learned you don't have to remember things perfectly." She stopped, considering, then brightened. "Ever heard of those alien abductees? They don't remember anything until they get hypnotized. This is kind of the same idea."

"You're going to hypnotize me?"

"No!" Again, Mikoto threw up her hands. "Okay, okay," she murmured. "Remember. He's an idiot, so just take things slow…"

"Ever thought about a career in teaching? You'd be great with the kids."

"Shut up," Mikoto said absently. "How do I…oh, right." She paused for a second more and nodded, before looking at Kamijou. "Your brain," she said, "remembers things you don't. One detail will lead to another, then another, then another…"

"You couldn't have told me that without the verbal abuse?"

"Ends justify the means, buddy."

This was impossible. It had to be. But as Kamijou kept listening to Mikoto's words, they started sounding less like the work of some crackpot sci-fi author, and more…well, more like the theories of a scientist who knew what she was talking about.

Besides, she had done this before…right?

"Hey," Mikoto said suddenly, interrupting Kamijou's thoughts. "You know you don't have to do this if you don't want to, right?" She laughed quietly. "I won't be disappointed or anything. I know I got pretty excited just now, but it's still your choice."

"No, I get that." Kamijou didn't want to answer immediately—he wasn't sure what would come out of his mouth. "And to be honest…" He looked over at Mikoto one more time.

How many times had this girl come to his rescue? How many times had she backed him up? How many times, in each case, had she used her powers flawlessly and in amazing ways?

"I think," Kamijou said finally, "that if it's you, I'll be okay with it." He smiled. "Let's do this."


End file.
